Stamp mill



June 16, 1942. G. H. GRusg 2,286,728.

sum? MILL Filed Ndv. 25. 1940 2 $heets-Sheet 1 l INVENTOR.

ATTORNEY-S.

Patented June 16, 1942 UNETE gr gimg EIQE 3 Claims.

' vide a stamp mill in which the weight of the stamp in its downward or crushing stroke is assisted by air under pressure trapped in a cylinder and piston device of the air spring type. This permits the stamps, and also the entire machine, to be made much lighter than is customary, thereby effecting a reduction in cost of manufacture, and making the machine more easily portable.

Another object, of the invention is to provide a stamp mill in which the stamps operate faster than is customary. This also is a result of the use of air springs to assist the weight of the stamps, thereby permitting lighter stamps with less inertia and consequently greater speed or frequency of movement.

Another object is to provide for adjustment of the blows struck by the stamps, so that lighter blows can be struck when crushing softer rock, and harder blows when crushing harder rock. By such adjustment the fineness of the crushed rock can be kept approximately constant regardless of its hardness, a great advantage in crushing ore for subsequent separating treatment. Adjustment of the force of the blows is simply provided by changing the pressure of the trapped air in the air springs.

Still further objects and advantages of the invention will become apparent from the following specification, which should be read with the understanding that changes, within the limits of the claims hereto appended, may be made in the form, construction and arrangement of the several parts herein shown and described, without departing from the spirit of the invention as defined in said claimsl A preferred embodiment of the invention will now be described with reference to the accompanying drawings wherein Fig. 1 is a front elevation of the machine, one of the air springs being shown in section.

Fig. 2 is a side elevation as viewed from the left hand side of Fig. 1.

In the drawings, the reference numerals 3' designate upright frame members, preferably wood, supported by a base 4 and joined together by horizontal frame members 5. The stamps 6, in the form of hollow vertical rods slidably mounted in suitable guides (not shown) in the cross members 5, are provided at their lower ends with removable shoes I which drop upon dies or crushing blocks 8 supported by the base 4, the

shoes 1 and dies 8 being positioned within a crushing box 9. Thereare two stamps shown in the maclnne herein illustrated, but any desired number consistent with good mechanical design can be used.

A mechanical feeding device of anyusual and suitable type, indicated at I0, feeds the ore into the top of the crushing box 9, and the crushed ore flows or is washed out through a front opening 9! into a chute 12. A system of levers and slides, indicated at l3, operates the feeder ID from one of the stamps 8 in the usual manner.

A horizontal shaft l4, mounted in journal boxes i5 supported in notches in the frame up- 1 rights 3, carries cams it, there being one cam for each stamp. The cams i6 engage the lower ends of collars ll adjustably secured upon the stamps 6 by keys l8. As the shaft [4 rotates, the cams It alternately raise the stamps 6 and allow them to drop. The shaft [4 is driven in any suitable manner, as for exampleby a belt i9 and pulleys from a drive shaft 2l.' So much is usual construction in a stamp mill, except that the stamps are customarily made solid to increase their weight.

My improvement lies in making the stamps 6 hollow in order to reduce their weight, and in assisting their downward crushing strokes by means of air springs now to be described.

A yoke 22 made of strap metal is bolted as at 23 to the top of each frame upright 3 and extends upwardly therefrom. Within the top portion of each yoke 22 is a block 24 having a spherical socket 25 in its lower side. An air. spring having a cylinder 26 is positioned vertically within each yoke 22, the cylinder 26 having an upper head 27 provided with an exterior lug 28 formed with a spherical upper end seated Within the socket 25. Thus the air spring cylinder bears upwardly against the yoke 22 with a ball and socket seat which permits lateral movement of the lower end of the cylinder in order to prevent binding of the piston and rod.

The air spring cylinder 23 contains a piston 29 having cup leathers 30 or other forms of packing. A rod 3| is secured to the piston 29 and extends downwardly slidably through a lower head 32 which acts as a guide for said piston rod. The lower end of the rod is rounded and seats within a spherical socket 33 formed on a lever 34. The outer end of said lever is pivoted at 35 to a bracket 36 bolted to the frame upright 3, and the inner end of said lever is bifurcated to form a yoke 31 which straddles the stamp 6 and bears downwardly upon a collar 38 adjustably secured thereon by a set screw 39.

Oil is introduced into the air spring cylinder 26 through a plug 40, preferably to the level of the broken line 4|, to assist in sealing the piston against leakage of air. Air is then forced into the upper portion of the cylinder 26 through a check valve 42 (which may be similar to an ordinary tire valve) to whatever pressure may be desired.

It will be apparent from Fig. 1 that as the cam l6 lifts the stamp 6, the lever 34 raises the piston 29 against the air pressure within the cylinder 26, and that when the point of the cam passes out from beneath the collar H, the air pressure within said cylinder assists the weight of the stamp in forcing it down. The stamp will therefore deliver a harder blow than it would if impelled downward by its weight alone. Conversely, a blow of given force can be delivered by a stamp of lighter weight than would be possible without the assistance of the air spring. Thus light stamps can be used, with a consequent saving in weight for the whole machine. Furthermore, because of the reduction in weight, i. e. mass, of the stamps, there is less inertia to overcome in starting both upward and downward strokes, and a higher speed is therefore possible.

The air pressure Within the cylinders can be adjusted to cause the stamps to deliver whatever means for raising said stamp and releasing it to drop by gravity, a cylinder containing trapped air under pressure, means for holding said cylinder against longitudinal movement, a piston movable in said cylinder, a lever having a fulcrum at one end and a forked opposite end, a piston rod connecting said piston with said lever between said ends, and a collar on said stamp, the forked end of said lever embracing said stamp and resting upon said collar, said lever moving said piston with said stamp whereby the expansive force of said trapped air is added to the force of gravity when said stamp drops.

2. In a stamp mill, a movable stamp, means for moving said stamp, a lever engaging said stamp for movement therewith, said lever having a fulcrum and a cup-shaped socket, a fixed member having a cup shaped socket facing said lever socket and spaced therefrom, a cylinder positioned between said sockets and containing trapped air under pressure, a head closing one end of said cylinder, said head having an exterior rounded portion seated in one of said sockets, a piston movable in said cylinder, the air within said cylinder being trapped and compressed between said piston and said head, and a rod connected with said piston and extending movably from the other end of said cylinder, said rod having a rounded end seated within the other of said sockets.

3. In a stamp mill, a frame, a stamp movable therein, means for moving said stamp, a movable lever having a fulcrum at one end and having its other end engaging said stamp said lever having a cup-shaped socket between its ends, a stationary member mounted on said frame having a cup-shaped socket facing the first mentioned socket and spaced therefrom, and an air spring mounted between said sockets, said air spring having relatively movable end members formed with exteriorly rounded portions seated within said sockets.

GEORGE H. GRUSS. 

